I am living with a roommate that I would like to kick out & am wondering how to do it and if I have the right?

I moved into my 3 bedroom apartment in November with a girlfriend of mine. My dad is the co-signer on the lease, I am on the lease and so is she. We have been having problems with her paying the cable bills and she is also just a very horrible roommate. She goes in to my room and goes through my things and also smoke pot all the time and has completely taken over the apartment. We now have a third roommate that is currently trying to get on the lease. I have talked to my property management company and they say my dad as the co-signer has the right to kick her out but I'm not sure if we have the right. She has been paying rent to date but has currently lost her job. The rent comes out of my bank account and my roommates pay me in cash and I put it back in. So I have been covering for her bills. I'm at a loss as to what to do. Can someone clarify things or give any advice? Thank you!